Site-specific investigation, risk assessment and clean-up of an inactive mine site in the Chilean Andes

摘要

Mina Marte, a gold mine operated between 1988 and 1993, was located in an environmentally-sensitive area of the Chilean Andes. Subsequent to the closing of the mine, limited clean-up activities were conducted, however, no formal mine closure plan was implemented. After a ten-year care and maintenance period and subsequent to acquiring the property in the mid-1990s, Teck Resources conducted an environmental site reconnaissance, which revealed that the site was in a condition that did not conform to Teck's environment, health and safety policies and standards. Activities conducted from 2007 through 2008 included the conduct of: a detailed site investigation; an ecological and human health risk assessment; and site clean-up activities. The detailed site investigation involved the collection and analysis of over 85 samples of soil, sediment, surface and ground water, and site materials. This investigation indicated that concentrations of metals, cyanide and hydrocarbons were above background concentrations, and in some cases, exceeded applicable environmental quality guidelines. An ecological and human health risk assessment was conducted, in conjunction with a targeted clean-up programme. Areas with elevated hydrocarbons in soil were cleaned up, and the risk assessments focused on metals and cyanide. Concentrations of metals were generally limited in spatial extent, and were low relative to North American guidelines. The ecological component of the risk assessment concluded that the estimated risks to terrestrial and aquatic receptors were low. The human health component of the risk assessment concluded that clean-up workers exposed to maximum concentrations through soil ingestion, dermal contact or dust inhalation were potentially at risk, but these risks could easily be mitigated to acceptable levels through the use of personal protective equipment. Site clean-up activities were conducted between 2007 and 2009, and included: the recycling of scrap metals from the site, completion of infrastructure demolitions, and reparation of surface water controls that had been damaged through vandalism. The works conducted at the property restored site conditions to Teck environmental standards, and would also be acceptable by international best practice standards.